Rotary steerable drilling system

Abstract

A rotary steerable drilling system includes a gear box driven by a driveshaft having an input rotatable in a first direction and an output rotatable in an opposite direction. An output of the gear box has a first axis of rotation, and a rotatable tubular bit sleeve annularly arranged around a distal portion of the driveshaft is pivotable to have a second axis of rotation and includes a connector assembly on a distal end of the bit sleeve for coupling the bit sleeve to a drill bit. A spherical CV joint couples the bit sleeve to the drive-shaft, eccentric cams are movably positioned on the driveshaft, a differential gearing system is connected to the eccentric cams, and a pressure applying device is connected to the eccentric cams. When activated, the pressure applying device applies pressure to modify the speed of rotation of the eccentric cams. A method of rotary steerable drilling is disclosed.

What is claimed is: 
     
       1. A rotary steerable drilling system positionable on a rotatable drill string in a wellbore, said rotary steerable system comprising:
 a gear box driven by a rotatable driveshaft coupled to the rotatable drill string, said gearbox having a rotary input rotatable in a first rotary direction and a rotary output rotatable in second rotary direction opposite to the first rotary direction; 
 the rotatable driveshaft having a first axis of rotation; 
 a pivotable rotatable tubular bit sleeve coupled at a first end to a second end of the rotatable drive-shaft, the bit sleeve pivotable to have a second axis of rotation different than the first axis of rotation of the rotatable driveshaft, said pivotable rotatable tubular bit sleeve including a connector assembly on a distal end of the bit sleeve for coupling the bit sleeve to a drill bit; 
 eccentric cams movably positioned concentrically around the drive-shaft; 
 a differential gearing system connected to the eccentric cams; and 
 pressure applying device connected to the eccentric cams, wherein when activated the pressure applying device applies pressure to modify a speed of rotation of the eccentric cams thereby pivoting the bit sleeve to the second axis of rotation. 
 
     
     
       2. The rotary steerable drilling system of  claim 1 , wherein a spherical constant velocity joint couples the tubular bit sleeve to the rotatable driveshaft. 
     
     
       3. The rotary steerable drilling system of  claim 1 , wherein the gearbox comprises a two-stage planetary gear box having a first stage planetary gear system, said first stage having a rotary input coupled to the rotatable driveshaft, said rotary input rotatable in a first rotary direction and a first rotary speed, and said first stage planetary gear system having an output in a second rotary direction opposite to the first rotary direction and at a second rotary speed, said two-stage planetary gearbox having a second stage planetary gear system having an input coupled to the output of the first stage planetary gear system, said second stage planetary gear system having an output in the second rotary direction of the first stage planetary gear system and an output rotary speed substantially equal to the first rotary speed of the first stage planetary gear system. 
     
     
       4. The rotary steerable drilling system of  claim 3 , wherein a portion of the driveshaft is contained within an annular stationary housing containing the gearbox and differential gearing system. 
     
     
       5. The rotary steerable drilling system of  claim 4 , wherein the annular stationary housing comprises a geostationary nonrotating section. 
     
     
       6. The rotary steerable drilling system  claim 3 , wherein the two-stage planetary gearbox has an input to output ratio of 1:−1. 
     
     
       7. The rotary steerable drilling system of  claim 1 , wherein the pressure applying device is selected from a group consisting of solenoids, hydraulic pistons, friction clutches, and actively controlled brakes. 
     
     
       8. The rotary steerable drilling system of  claim 1 , wherein the differential gearing system further comprises a first sun gear connected to a drive for an inner cam, and a second sun gear connected to a drive for an outer cam, and the first and second sun gears are connected by a planet gear. 
     
     
       9. The rotary steerable drilling system of  claim 8 , wherein the pressure applying device comprises a first solenoid connected to the drive for the inner cam, and a second solenoid connected to the drive for the outer cam. 
     
     
       10. The rotary steerable drilling system of  claim 9 , wherein either of the solenoids impart force to its respective cam drive when the solenoid is energized. 
     
     
       11. The rotary steerable drilling system of  claim 9 , wherein the eccentric cams are located within a rotatable sleeve. 
     
     
       12. The rotary steerable drilling system of  claim 9 , wherein the solenoids are annular and disposed around the respective eccentric cams. 
     
     
       13. A method of rotary steerable drilling comprising:
 positioning a rotary steerable drilling system on a distal end a rotatable drill string in a wellbore; 
 rotating an input of a gear box with a rotatable driveshaft in a first rotary direction; 
 outputting from the gear box a rotary output in second rotary direction opposite to the first rotary direction 
 about a first axis of rotation; 
 pivoting with a differential gearing system a rotatable tubular bit sleeve annularly arranged around a distal portion of the driveshaft by activating a first pressure applying device and a second pressure applying device connected respectively to a first eccentric cam and a second eccentric cam movably positioned on the driveshaft, wherein pressure applied to each eccentric cam modifies a respective speed of rotation of each of the eccentric cams, thereby pivoting the bit sleeve to a second axis of rotation; and 
 rotating a drill bit attached to a distal end of the tubular bit sleeve. 
 
     
     
       14. The method of  claim 13  wherein rotating an input of a gear box with the rotatable driveshaft in a first rotary direction and outputting a rotary output in second rotary direction opposite to the first rotary direction further comprises:
 providing a two-stage planetary gear box having a first stage planetary gear system, wherein said first stage planetary gear system includes a rotary input coupled to the rotatable driveshaft and said two-stage planetary gearbox-having a second stage planetary gear system having an input coupled to the output of the first stage planetary gear system; 
 rotating the rotary input of the first stage gear system in a first rotary direction and at first rotary speed, and outputting from the first stage planetary gear system an output in a second rotary direction opposite to the first rotary direction and at a second rotary speed; 
 inputting into the second stage gear system coupled to the output of the first planetary stage gear system the output of the first stage planetary gear system; and 
 outputting from the second stage gearing system an output rotary speed substantially equal to the first rotary speed of the first stage planetary gear system and in an opposite direction from the first rotary direction of the first stage planetary gear system. 
 
     
     
       15. The method of  claim 14 , further including enclosing a portion of the driveshaft and gearing elements in an annular stationary housing. 
     
     
       16. The method of  claim 15 , wherein the annular stationary housing comprises a geostationary nonrotating section. 
     
     
       17. The method of  claim 14 , wherein the two-stage planetary gearbox has an input to output ratio of 1:−1. 
     
     
       18. The method of  claim 13 , wherein the pressure applying device is selected from a group consisting of solenoids, hydraulic pistons, friction clutch, and actively controlled brake. 
     
     
       19. The method of  claim 13 , wherein the differential gearing system comprises a first sun gear connected to a drive for an inner cam, and a second sun gear connected to a drive for an outer cam, and the first and second sun gears are connected by a planet gear. 
     
     
       20. The method of  claim 19 , wherein the pressure applying device comprises a first solenoid connected to the drive for the inner cam, and a second solenoid connected to the drive for the outer cam. 
     
     
       21. The method of  claim 20 , further including energizing either of the solenoids and there by applying force to their respective cam. 
     
     
       22. The method of  claim 20 , wherein the solenoids are annular and disposed around each respective eccentric cam. 
     
     
       23. The method of  claim 13 , wherein the eccentric cams are located within a rotatable sleeve.